Implementing and simulating the water isotopes (δ18O and δD) distribution in the Mediterranean Sea using a high-resolution oceanic model

Water isotopes are one of the most widely used proxies in ocean climate research. However, there are still gaps in our understanding of the processes that control their composition.  Compared to other large ocean basins, the Mediterranean is ideally suited to improve our understanding of the processes influencing and driving oxygen isotopic variability, and to refine the current modelling approach. For the first time in a high-resolution Mediterranean dynamical model (NEMO-MED12), stable water isotopes (δ¹⁸O and δD) were successfully implemented and simulated in the whole basin. The well-known east-west gradient of δ¹⁸O in Mediterranean water masses is successfully simulated by the model. Results also show good agreement between simulated and observed δD. δD shows a strong linear relationship with δ¹⁸O (r² = 0.98) and salinity (r² = 0.94) for the entire Mediterranean basin. Furthermore, the modelled δ¹⁸O/salinity relationships are in good agreement with observations, with a weaker gradient simulated in the eastern basins than in the western basins. We investigate the relationship of the isotopic signature of the CaCO₃ shell (δ18Oc) with temperature and the influence of seasonality. Our results suggest a more quantitative use of δ¹⁸O records, combining reconstruction with modelling approaches. This opens up broad perspectives for paleoclimate-related applications.